Originally by Ximian, it was later acquired by Novell, and is now being led by Xamarin, a subsidiary of Microsoft and the .NET Foundation.

Xamarin is a Microsoft-owned San Francisco-based software company founded in May 2011 by the engineers that created Mono, Xamarin.Android (formerly Mono for Android) and Xamarin.iOS (formerly MonoTouch), which are cross-platform implementations of the Common Language Infrastructure (CLI) and Common Language Specifications (often called Microsoft .NET).

When Microsoft first announced their .NET Framework in June 2000 it was described as "a new platform based on Internet standards", and in December of that year the underlying Common Language Infrastructure was published as an open standard, "ECMA-335", opening up the potential for independent implementations.

The .NET Framework, .NET Core, Mono, DotGNU and Portable.NET are implementations of the CLI.

Windows Forms 2.0 is also supported, but not actively developed, and as such its support on Mono is incomplete.

Windows Forms (WinForms) is a graphical (GUI) class library included as a part of Microsoft .NET Framework or Mono Framework, providing a platform to write rich client applications for desktop, laptop, and tablet PCs.

An open-source implementation of Microsoft Silverlight, called Moonlight, has been included since Mono 1.9.

Moonlight is a free and open source implementation of the now deprecated Microsoft Silverlight application framework for Linux and other Unix-based operating systems, developed and then abandoned by the Mono Project.

Originally by Ximian, it was later acquired by Novell, and is now being led by Xamarin, a subsidiary of Microsoft and the .NET Foundation. Miguel de Icaza of Ximian believed that .NET had the potential to increase programmer productivity and began investigating whether a Linux version was feasible.

In May 2011 The Attachmate Group laid off all its US staff working on Mono, which included De Icaza.

CIL is a CPU- and platform-independent instruction set that can be executed in any environment supporting the Common Language Infrastructure, such as the .NET runtime on Windows, or the cross-platform Mono runtime.

It uses MonoTouch to produce native iOS applications for iPhone, iPad, and iPod touch, Mono for Android to creating native Android applications, and ASP.NET to support HTML5 apps using AJAX, CSS, and JavaScript.

Within a native .NET/Mono application, all code is managed; that is, it is governed by the CLI's style of memory management and thread safety.

Managed code is computer program code that requires and will execute only under the management of a Common Language Infrastructure (CLI) Virtual Execution System (VES) virtual machine, e.g. .NET Core CoreFX, .NET Framework Common Language Runtime (CLR), or Mono.

MonoDevelop is a free GNOME integrated development environment primarily designed for C# and other .NET languages such as Nemerle, Boo, and Java (via IKVM.NET), although it also supports languages such as C, C++, Python, and Vala.

Nemerle is a general-purpose high-level statically typed programming language designed for platforms using the Common Language Infrastructure (.NET/Mono).

MonoDevelop is a free GNOME integrated development environment primarily designed for C# and other .NET languages such as Nemerle, Boo, and Java (via IKVM.NET), although it also supports languages such as C, C++, Python, and Vala.

IKVM.NET is an implementation of Java for Mono and the Microsoft .NET Framework.

Some programs written for the Linux Desktop include Banshee, Beagle, F-Spot, Gbrainy, Docky/GNOME Do, MonoTorrent, Pinta, and Tomboy. In November 2011 at a Ubuntu Developer Summit, developers voted to have the Mono-based Banshee media player removed from Ubuntu's default installation beginning on Ubuntu 12.04; although reported reasonings included performance issues on ARM architecture, blocking issues on its GTK+ 3 version, and it being, in their opinion, "not well maintained", speculation also surfaced that the decision was also influenced by a desire to remove Mono from the base distribution, as the remaining programs dependent on Mono, gbrainy and Tomboy, were also to be removed.

Built upon Mono and Gtk#, it uses the GStreamer multimedia platform for encoding and decoding various media formats, including Ogg Vorbis, MP3 and FLAC.